Three of us have been practicing IF for some time. Son #3 lost half his body weight (300->150s), mostly under IF. It's his way-of-life now.

Son #5 and I have done well, losing about 30lbs ea.

For son #5 and I, calorie counts are integral to our weight loss (but weren't enough on their own). Conversely, calories don't seem to matter to son #3. He can eat mountains of whatever w/o blowing up his weight.

Thoroughly unsurprising. Because CICO is correct to a great extent. It’s just that for different people, different approaches to restricting calories in are more effective than others. I thought we’d figured this out by now.